Nanometric writing and erasure combined with supersensitive reading without erasure

ABSTRACT

A hollow, scanned probe tip is used to write and erase information in a material in manometric dimensionalities, as well as to provide ultrasensitive sensing of the stored information. The material is excited to alter it for writing and erasing, while sensing, or reading, of the stored information is accomplished by highly sensitive force sensing.

1. FIELD OF THE INVENTION

This invention deals with the area of high density optical memorieswhich can be extended to nanoswitches and nanoswitch arrays. The essenceof the invention is electrical, chemical, thermal, magnetic and/oroptical excitation of a material by a scanned probe microscope tip. Thematerial changes one of its characteristics as a result of theexcitation in a way that can be sensed by the supersensitive forcesensing capabilities of the scanned probe microscope tip and can bereversed at will with the same nanometric tip. The invention also can bereadily extended to the formation of nanoswitches and nanoswitch arrays.

2. BACKGROUND OF THE INVENTION

Scanned probe microscopes can potentially write and read informationwith nonometric precision and high density. A recent study has shown [S.Hoen, H. J. Mamin and D. Rugar, AppI. Phys. Lett. 64,267 (1994)] thatone of most sensitive ways to read information is by measuring analteration using the force sensing capabilities of the scanned probe tipthat imposed the change. However, this study also highlights the factthat using the approach of this study, which involved simply heating thesurface and imposing a local structural change, it is not possible toreverse the process and make a write, read and erase cycle. The presentinvention focuses on an approach that indicates how such a write, readand erase cycle could be completed. This also leads to nanoswitches andnanoswitch arrays.

3. STATE OF PRIOR ART

There is no invention in the prior art that describes a process forwrite, read and erase high density memories or ultrasensitive switchesthat were able to use the supersensitive capabilities of force sensingof the imposed change using scanned probe techniques.

4. SUMMARY OF THE INVENTION

A method and a device that permits the erasable recording of informationin nanometric dimensionalities using a scanned probe tip. The changesare then sensed by the supersensitive capabilities of the force sensingattributes of the tip. Subsequently the written information can beerased with one of the attribute of the same probe. The invention allowsthe separation of the writing and the erasing operation from thesupersensitive reading operation. The invention can also formsupersensitive nanoswitches and nanoswitch arrays.

5. DESCRIPTION OF THE INVENTION

The invention is illustrated in the accompanying drawings, in which:

FIG. 1 illustrates a cantilevered tip in contact or near-contact with amaterial; and

FIG. 2 illustrates a nanoswitch utilizing the features of the invention.

The invention consists of a method and a device that permits nanometricrecording, reading and erasing of changes in a material using themultifunctional capabilities of a tip of a scanned probe microscope. Thesame principles could also be used to produce supersensitivenanoswitches and nanoswitch arrays.

5.1 Write, Erase and Supersensitive Reading in Ultrahigh Density OpticalMemories

The method and the device consists of a tip 1.1 connected to acantilever 1.2 which is in nearcontact or contact with a material 1.3. Atip is chosen having the capability of emitting a spot of light, ofacting as one electrode to impose an electrical field on the material,of delivering material through a hollow orifice force sensing element,of imposing heat on the sample while simultaneously imposing a magneticfield, or of imposing or a force on the material. The tip also has theability to monitor the change that it has imposed using itssupersensitive force sensing capabilities. As a result of one or more ofthese excitation methods the material alters its charge characteristics,its volume, its light emission characteristics, etc., and then thischange is detected with supersensitive force sensing attribute of thetip. The object is to bypass problems of erasure of the written materialand to use the most sensitive aspect of the tip for detection of thewritten material. The material also would have the capability of havingits alteration erased by one or more of the attributes of the tipunrelated to the reading attribute of monitoring the change imposed bythe excitation using the supersensitive force sensing.

In one example the tip could deliver light in a very local region usingnear-field optical microscopy and this would change the volume or thecharge properties of the material that would be detected by the forcesensing capabilities of the same tip. The volume or charge change wouldbe stable until a second pulse of light would be imposed on the samepixel to erase the volume change that was generated in the material bythe first pulse of light. In another example the tip could produce anelectrical pulse that would then cause a volume change or an electricalchange, such as a volume change or a change in surface charge, in thematerial which would be sensed by the supersensitive force sensingcapabilities of the same tip.

This approach separates the excitation from a supersensitive detectionevent and permits detection of the change without erasure. It alsopermits a reversal of the volume change with the reverse of theexcitation process and therefore permits erasure of the alteration. Sucha device reaches an ideal of super-resolution read, write and erasememory.

An example of a material that could be used in this scheme would be afilm of a protein that could change its volume with one or another ofthe excitation mechanisms. A specific example of such a protein isbacteriorhodopsin which can change its volume with light. Such a systemalso has the potential of changing its charge characteristics withexcitation that may also include electrical excitation.

Another example would be a tip that was capable of heating and imposinga magnetic field on a magnetic material that would then change the forcethat it would impose on the tip. An example of how to generate such atip is based on a recent study [G. Fish, O. Bouevitch, S. Kokotov, K.Lieberman, D. Palanker, I. Tutovets and A. Lewis, Rev. Sci. Instr. 66,3942-3948 (1995)]. Although this study did not envision this invention,the techniques in this paper could be used to generate a tip with amagnetic material within the hollow tube of a tapered, cantileveredcapillary that could be used to either impose heat and a magnetic fieldon a magnetic surface in order to write or erase and could monitor withthe tip the change in the magnetic surface.

The above are simply some examples of a variety of combinations ofexcitation, the reversal of excitation and super-sensitive reading usingforce sensing.

5.2 Nanoswitches

The method and the device consists of a tip 2.1 connected to acantilever 2.2 which is in near-contact or contact with a material 2.3.A tip is chosen having the capability of emitting a spot of light, ofacting as one electrode to impose an electrical field on the material,of delivering material through a hollow orifice sensing element, ofimposing heat on the sample while simultaneously imposing a magneticfield, or of imposing a force on the material. As a result of one ofthese multifunctional attributes of the tip, the material alters itscharge characteristics, its volume, etc. and then this change isdetected with the supersensitive force sensing attribute of the tip. Thechange in the position of the cantilever with the material alterationresults in the cantilever making contact with another point 2.4. Thematerial also would have the capability of having its alteration erasedby one or more of the attributes of the tip related or unrelated to theexcitation attribute. The microfabrication of arrays of suchnanoswitches can be envisioned.

6. ADVANTAGES OVER PRIOR ART

No combination that would allow for writing, supersensitive reading andmaterial erasure has been found as of yet and no nanoswitches of thetype we envision in this invention have been devised.

7. APPLICATIONS

One principal application is of course very high density opticalmemories. However, in addition to this, nanoswitches could beconstructed in this way in which the tip excites a structural change ina material and this structural change alters the position of thecantilever that allows it to either be in electrical contact with apoint or to be out of contact with this point. in addition, arrays ofnanoswitches of the type described in this invention could also bemicrofabricated and these arrays could be used in a variety ofapplications including neural network implementations.

What is claimed is:
 1. A device for recording, detecting and erasinginformation in nanometric dimensionalities, comprising: a materialcapable of alteration in nanometric dimensionalities; a scanned probemicroscope having a cantilevered tip element with multifunctionalcapabilities providing excitation of said material for altering thematerial, said element having supersensitive force sensing capabilitiesfor also sensing such alteration of said material, wherein alterationsof said material are erasable by said tip element using a variant of theexcitation causing said alteration.
 2. The device of claim 1, whereinsaid variant of the excitation for erasing said alterations is distinctfrom the force sensing capabilities of said tip element.
 3. The deviceof claim 2, wherein the excitation of said material and the variant ofthe excitation are each selected from the group consisting of optical,electrical, chemical, thermal, magnetic, and pressure excitation.
 4. Thedevice of claim 1, further including a second cantilevered element, andwherein said variant of the excitation is provided by said secondcantilevered element for erasing said alterations.
 5. The device ofclaim 4, wherein the excitation of said material and the variant of theexcitation are each selected from the group consisting of optical,electrical, chemical, thermal, magnetic and pressure excitation.
 6. Adevice for recording, detecting and erasing information in nanometricdimensionalities, comprising: a material capable of alteration innanometric dimensionalities; a scanned probe microscope having acantilevered element with multifunctional capabilities providingchemical excitation of said material for altering the material, saidelement having supersensitive force sensing capabilities for alsosensing such alteration of said material, wherein alterations of saidmaterial are erasable by a variant of the excitation causing saidalteration.
 7. A device for recording, detecting and erasing informationin nanometric dimensionalities, comprising: a material capable ofalteration in nanometric dimensionalities; a scanned probe microscopehaving a cantilevered element with multifunctional capabilitiesproviding excitation of said material by pressure for altering thematerial, said element having supersensitive force sensing capabilitiesfor also sensing such alteration of said material, wherein alterationsof said material are erasable by a variant of the excitation causingsaid alteration.
 8. A device for recording, detecting and erasinginformation in nanometric dimensionalities, comprising: a materialcapable of alteration in nanometric dimensionalities; a scanned probemicroscope having a cantilevered element with multifunctionalcapabilities providing excitation of said material for altering thematerial; a nanoswitch having a first contact on said cantilever and asecond contact adjacent to said cantilever; said cantilever elementhaving a force sensing tip responsive to alteration of said material tocause said cantilever to cause said first and second nanoswitch contactsto open or close.
 9. A device as in claim 8 in which the excitation ofthe nanoswitch is optical.
 10. A device as in claim 8 in which theexcitation of the nanoswitch is electrical.
 11. A device as in claim 8in which the excitation of the nanoswitch is chemical.
 12. A device asin claim 8 in which the excitation of the nanoswitch is thermal.
 13. Adevice as in claim 8 in which the excitation of the nanoswitch isthermal and/or magnetic.
 14. A device as in claim 8 in which theexcitation of the nanoswitch is pressure.
 15. A device as in claim 8which is part of an array of nanoswitches.
 16. A device as in claim 9which is part of an array of nanoswitches.
 17. A device as in claim 10which is part of an array of nanoswitches.
 18. A device as in claim 11which is part of an array of nanoswitches.
 19. A device as in claim 12which is part of an array of nanoswitches.
 20. A device as in claim 13which is part of an array of nanoswitches.
 21. A device as in claim 14which is part of an array of nanoswitches.
 22. A method for producing,detecting and selectively erasing information in nanometricdimensionalities, comprising: providing a material capable of alterationin nanometric dimensionalities; exciting and thereby altering saidmaterial by a cantilevered element with multifunctional capabilities ina scanned probe microscope, said cantilevered element including asupersensitive force sensing tip; sensing the alteration of saidmaterial with said tip; and selectively erasing said alteration of saidmaterial by supplying with said tip a variant of the excitation whichcaused the alteration of the material.
 23. The method of claim 22,wherein the steps of exciting and thereby altering said material and ofselectively erasing said alteration are each selected from the groupconsisting of optical, electrical, chemical, thermal, magnetic, andpressure excitation.
 24. The method of claim 22, wherein selectivelyerasing said alteration of said material includes using a variant of theexcitation by said cantilevered element which is distinct from thesensing of the alteration.
 25. A method for producing, detecting andselectively erasing information in nanometric dimensionalities,comprising: providing a material capable of alteration in nanometricdimensionalities; chemically exciting and thereby altering said materialby a cantilevered element with multifunctional capabilities in a scannedprobe microscope, said cantilevered element including a supersensitiveforce sensing tip; sensing the alteration of said material with saidtip; and selectively erasing said alteration of said material using avariant of the chemical excitation which caused the alteration of thematerial.
 26. A method for producing, detecting and selectively erasinginformation in nanometric dimensionalities, comprising: providing amaterial capable of alteration in nanometric dimensionalities; excitingby applying pressure and thereby altering said material by acantilevered element with multifunctional capabilities in a scannedprobe microscope, said cantilevered element including a supersensitiveforce sensing tip; sensing the alteration of said material with saidtip; and selectively erasing said alteration of said material using avariant of the pressure excitation which caused the alteration of thematerial.
 27. A method for producing, detecting and selectively erasinginformation in nanometric dimensionalities, comprising: providing amaterial capable of alteration in nanometric dimensionalities; excitingand thereby altering said material by a cantilevered element withmultifunctional capabilities in a scanned probe microscope, saidcantilevered element including a supersensitive force sensing tip;sensing the alteration of said material with said tip to producecorresponding motion in said cantilevered element; activating ananoswitch in response to said motion of said cantilevered element; andselectively erasing said alteration of said material using a variant ofthe excitation which caused the alteration of the material.
 28. A methodas in claim 27, wherein excitation of said material and correspondingactivation of said nanoswitch is optical.
 29. A method as in claim 27,wherein excitation of said material and corresponding activation of saidnanoswitch is electrical.
 30. A method as in claim 27, whereinexcitation of said material and corresponding activation of saidnanoswitch is chemical.
 31. A method as in claim 27, wherein excitationof said material and corresponding activation of said nanoswitch isthermal.
 32. A method as in claim 27, wherein excitation of saidmaterial and corresponding activation of said nanoswitch is thermaland/or magnetic.
 33. A method as in claim 27, wherein excitation of saidmaterial and corresponding activation of said nanoswitch is pressure.34. A method as in claim 27, further including activating an array ofnanoswitches in response to alteration of said material.